We are investigating the chemical nature of the renal nerves. In a typical preparation using the technic of Karnovsky and Roots for acetyl-cholinesterase or the fluorescence histochemical technic of Falck et al. clusters of nerves are clearly seen immediately adjacent to glomeruli. We have developed a method for determination of the degree of innervation by counting the number of glomeruli showing adjacent clusters of nerves. It appears that an equivalent degree of innervation is demonstrated by either technic. Using this method we could evaluate the response of the renal nerves to 6-hydroxydopamine. One dose of the drug produces concomitant decrease of the degree of innervation in the acetylcholinesterase positive nerves and in those shown by fluorescence histochemistry. Two doses of the drug reduce to one the degree of innervation shown by fluorescein histochemistry and to less than 1% that observed with the acetylcholinesterase technic; 60HDA destroys selectively the adrenergic nerve terminals. These results therefore indicate that acetyl-cholinesterase is present in the renal adrenergic nerves. BIBLIOGRAPHIC REFERENCES: Bennett, C.M, Barajas, L. and Wilburn, R.L.: Effect of Beta-Adrenergic Blockade on Renal Renin Release and Synthesis. Submitted for presentation at the Fourth Meeting of the International Society of Hypertension, Sydney, Australia, February 24-26, 1976. Barajas, L., Wang, P. and De Santis, S.: Correlative Histochemical and Ultrastructural Studies on the Rat Renal Nerves. In: Abstracts of Papers Presented at the Seventh Joint Meeting of the Northern and Southern California Societies for Electron Microscopy, San Diego, California, May 2-3, 1975.